WO2019035580A1

WO2019035580A1 - Method for producing negative electrode active material for lithium secondary battery, and lithium secondary battery including same

Info

Publication number: WO2019035580A1
Application number: PCT/KR2018/008762
Authority: WO
Inventors: 안정철; 박세민; 이재은; 김병주; 유승재; 김형근; 이상은; 이찬우; 조현철; 김명기
Original assignee: 주식회사 포스코; 재단법인 포항산업과학연구원; (주)포스코켐텍
Priority date: 2017-08-17
Filing date: 2018-08-01
Publication date: 2019-02-21
Also published as: EP3670475A4; US20210143425A1; JP2020532058A; CN111225888A; KR20190019430A; EP3670475A1

Abstract

Presented is a method for producing a negative electrode active material which has a high discharge capacity, a high charge-discharge efficiency, and excellent high-output characteristics, and which experiences only a small volume change during charging/discharging. A method for producing a negative electrode active material for a lithium secondary battery according to an embodiment of the present invention comprises: a step for producing primary particles by crushing a carbon raw material containing 4 to 10 wt% of volatile components; a step for producing secondary particles by mixing the primary particles with a binder; and a step for producing a graphite material by graphitizing the secondary particles.

Description

【Specification】

Title of the Invention

METHOD FOR MANUFACTURING ANNEALDEAL ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY

TECHNICAL FIELD

A negative electrode active material for a lithium secondary battery, and a lithium secondary battery comprising the same.

TECHNICAL BACKGROUND OF THE INVENTION

BACKGROUND ART [0002] In recent years, portable electronic devices such as mobile phones and tablet PCs have been increasing in capacity due to higher performance and increased power consumption due to functional integration, and electric power tools, especially HEVs (Hybrid Cars) and EVs The necessity of a secondary battery having a high output characteristic excellent in charging / discharging speed has been greatly increased. In addition, as the use time increases, the charging / discharging cycle of the battery is reduced and the life of the battery cycle is required to be greatly improved. Minimization of the volume change (expansion and contraction) .

Lithium secondary batteries are widely used because of their advantages such as high energy density and high voltage among secondary batteries, and commercial lithium secondary batteries generally employ cathode active materials of metal oxide system and carbonaceous anode active materials such as graphite.

Graphite, which is an anode active material, is mined from a mine, subjected to physical selection and high purity, and subjected to a heat treatment of a carbonaceous coke obtained by heat treating an organic matter such as natural carvings and coal or petroleum residues, .

The natural hctical anode material is advantageous in high capacity battery construction compared to artificial graphite, but has a problem of reducing capacity due to the progression of charge / discharge cycle. Natural corundum generally has a form of impression (plate shape). Therefore, in order to increase the filling density and improve the output characteristic in the production of electrodes, generally spheroidizat ion is used for processing. Milling (milling) is generally used in the process of spheroidizing the impression cylinder, It is known that the capacity is decreased during the layer discharging process of the battery due to the increase in the stress in the inside of the particle and the defect.

On the other hand, artificial carpets have a disadvantage in that the capacity is somewhat lower than natural carpets, and the price is high due to the manufacturing process cost, but the carpets have a merit of relatively long lifetime characteristics and are favored as materials for portable electronic devices that emphasize long life characteristics. At the same time, it is replacing natural rust. Generally, in order to manufacture artificial graphite anode materials, coal or petroleum residue black is manufactured through carbonization and high-temperature heat treatment (softening) process of the pitch, which is a processed product, and a small amount of a substance capable of catalytic graphitization to increase the capacity is added And a softening heat treatment process is applied. In order to compensate for the disadvantages of both materials depending on the purpose of use, composite anode materials in which natural graphite and artificial graphite are mixed are sometimes used. For example, a process for producing an anode material having high capacity, high output and long life characteristics has been proposed through a catalytic softening heat treatment using a catalyst material added after combining a spherical natural grain and a synthetic grain powder. In addition, a process for producing an anode material by combining the coke and the spheroidized natural wood chips, which are the raw materials of the synthetic wood lump, and then completing the final lump heat treatment has been proposed. A method of manufacturing a composite anode material by coating a natural graphite and an artificial graphite with a pitch material, carbonizing the carbonaceous layer, forming a carbonaceous layer on the surface, adding a catalyst, and finally performing a final graphitization heat treatment is proposed.

Generally, in order to increase the capacity of the artificial carburizing material, the graphitization heat treatment temperature is maintained at a high level to increase the softening degree, or the catalytic material is added for the catalytic graphitization induction. In order to improve the discharge efficiency of the layer, the surface coating of artificial carbohydrates minimizes the exposure of the edges of the particles on the particle surface through grinding, etc., so that the excessive formation of the passivated fi lm through electrolytic decomposition The use of suppression is also used. In order to improve the high-speed charging / discharging performance, there is a case where irregular adjustment of the mutual orientation of the graphite particles in the processed product of the artificial hue, or a carbonaceous coating is introduced on the particle surface. In order to reduce the change of the phosphorus content and the electrode volume due to charging and discharging, mutual orientation of graphite particles in artificial graphite processed product It is also possible to use irregular shapes or to increase the strength of the material itself to improve the dimensional stability during layer discharge. In addition to the above-mentioned cases, a variety of techniques have been developed to improve the performance of the battery material of synthetic hammocks. However, there is a trade-of-f relationship between the performance of the hammocks. For example, when the catalyst is introduced into the manufacturing process to increase the capacity, the porosity of the inside and the surface of the artificial graphite increases due to the pore generated during the thermal decomposition of the catalyst, and the surface area of the resulting graphite and the electrolyte And side effects of deterioration of the battery life characteristics are caused by the increase in the half strength. If the diffusion length of lithium ion is shortened by reducing the size of artificial graphite particles, the high-speed layer discharge characteristics can be improved, but the battery life may also decrease due to the increase of the specific surface area derived from small particle size. In order to suppress the change of the material and the electrode volume which occur during the discharge of the layer, in the case of forming a secondary particle type anode material in which particles of a small particle size are agglomerated and complexed to a certain size, primary particles The particles have a merit that the volume change of the electrode is reduced due to the offset of the material volume change due to the layer discharge. However, irregular orientation of the particles is not layered according to the processing form of the primary particles and the secondary granulation process conditions, and the specific surface area is increased or the secondary particle shape is uneven, And the battery life may be reduced.

DISCLOSURE OF THE INVENTION

[Problem to be solved]

A high discharge capacity, a high charging / discharging efficiency, an excellent high output characteristic, and a small volume change during discharging of a layer.

MEANS FOR SOLVING THE PROBLEMS

According to an embodiment of the present invention, there is provided a method of manufacturing an anode active material for a lithium secondary battery, comprising: preparing a primary particle by pulverizing a carbon raw material containing 4 to 10% by weight of volatile matter; Preparing secondary particles by coalescing the primary particles with a binder; And graphitizing the secondary particles to produce a hammered material.

The carbon source may include green coke or raw coke. The D50 particle size of the primary particles may be 10 [beta] eta or less.

The sphericity of primary particles is 0. 75 to < / RTI >

After the step of producing the primary particles, the step of finishing the primary particles may be further included.

After the step of preparing the primary particles, the method may further include a step of raising the primary particles at a rate of 1 to 10 t / min.

After the step of producing the primary particles, the step of heat-treating the primary particles may remove the volatile components in the primary particles.

In the step of removing the volatile matter in the 1 < th > -order particles, the heat treatment temperature may be 800 to 150CTC.

In the step of producing the secondary particles, 2 to 20 parts by weight of the binder may be mixed with 100 parts by weight of the primary particles.

The binder may include coal-based pitches or petroleum-based pitches.

The binder may have a softening point of 80 to 300 ° C.

The step of preparing the secondary particles may be carried out for 1 to 5 hours using a shear force at a silver of 110 to 500 ° C.

The D50 particle size of the secondary particles may be 14 to 25.

After the step of producing the secondary particles, the step of carbonizing the secondary particles may further include the step of carbonizing the secondary particles.

The carbonization step can be carried out at a temperature of 800 to 150 (TC.

The step of producing the graphite material can be carried out at a temperature of 2800 to 3200 ° C.

The prepared graphite sheet may have a specific surface area of 1.7 m ² / g or less, and a tap density

0 . 7 g / cc or more.

A lithium secondary battery according to an embodiment of the present invention includes: a positive electrode; cathode; And an electrolyte; and the negative electrode includes a negative electrode active material for a lithium secondary battery manufactured from the above-described recipe.

【Effects of the Invention】

The discharge capacity and the initial layer discharging efficiency are high when the negative electrode active material for a lithium secondary battery manufactured by the manufacturing method according to an embodiment of the present invention is used. At the same time, the electrode expansion due to the stratified charge discharge is low and the high-speed discharge characteristic is improved. BRIEF DESCRIPTION OF THE DRAWINGS

1 is a schematic flowchart of a method of manufacturing a negative electrode active material for a lithium secondary battery according to an embodiment of the present invention.

Fig. 2 is a scanning electron microscope (SEM) photograph of primary particles ground and ground in Example 1. Fig.

3 is a scanning electron microscope (SEM) photograph of the negative electrode active material prepared in Example 1. Fig.

4 is a scanning electron microscope (SEM) photograph of the primary particles pulverized in Example 3. Fig.

FIG. 5 is a scanning electron microscope (SEM) photograph of the primary particles pulverized and ground in Comparative Example 1. FIG.

DETAILED DESCRIPTION OF THE INVENTION

The terms first, second and third, etc. are used to describe various portions, components, regions, layers and / or sections, but are not limited thereto. These terms are only used to distinguish any moiety, element, region, layer or section from another moiety, moiety, region, layer or section. Thus, a first portion, component, region, layer or section described below may be referred to as a second portion, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified and that the presence or absence of other features, regions, integers, steps, operations, elements, and / It does not exclude addition.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Commonly used predefined terms are defined in the relevant technical literature and in the present disclosure Are interpreted as having a corresponding meaning, and are not to be construed as ideal or very formal unless defined otherwise.

In the present specification, the D50 particle diameter refers to the particle size of the active material particles having various particle sizes distributed in a volume ratio of 50%.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

FIG. 1 schematically shows a flowchart of a method of manufacturing a negative electrode active material for a lithium secondary battery according to an embodiment of the present invention. The flowchart of the method for producing the negative electrode active material for lithium secondary battery of FIG. 1 is for illustrating the present invention only, and the present invention is not limited thereto. Therefore, the manufacturing method of the negative electrode active material for a lithium secondary battery can be variously modified.

As shown in FIG. 1, a method for producing an anode active material for a lithium secondary battery includes the steps of (S10) producing a primary particle by pulverizing a carbon raw material containing 4 to 10% by weight of volatile matter, A step (S20) of producing secondary particles, and a step (S30) of producing a graphite by softening the secondary particles. In addition, if necessary, the manufacturing method of the negative electrode active material for a lithium secondary battery may further include other steps.

First, in step S10, a carbon raw material containing 4 to 10 wt% of volatile matter is pulverized to produce primary particles. Here, the volatiles (matter) are generally solid carbonaceous residues remaining in the carbon stock. Refers to a component that can be converted into a gas phase and separated from a carbon source when heated in an inert atmosphere by means of a low molecular weight organic compound. In one embodiment of the present invention, a carbon material containing an appropriate amount of volatile matter is used as a starting material. When a carbonaceous material such as calcined or carbonized material containing no or little volatile components is used as the carbon raw material, the particle surface becomes rough in the crushing step (S10) Exposure of the cross section increases. Ultimately, the specific surface area of the finally prepared negative electrode active material becomes large, The tap density becomes small, the rate of electrode expansion becomes large, and the high-speed discharge characteristic becomes poor. On the other hand, if the volatile content in the carbon raw material is too high, the affinity between the particle surface and the binder material during the preparation of the secondary particles may decrease, which may limit the increase of the particle size of the secondary particles produced. The particle porosity and the specific surface area may increase due to the generation of the inner and surface pores due to the generation of excessive volatiles.

Specifically, the carbon raw material may include green coke or raw coke. Green coke or raw coke can be produced from coal or petroleum residue, or processed product, through coking reaction under high pressure and high temperature conditions. Anisotropic or needle coke having a high carbon carbon texture orientation in a uniaxial direction or an isotropic or pitch coke having a low carbonaceous texture orientation may be obtained depending on the composition of the raw material and the caulking process conditions, tch coke) is obtained. Green or green is a state obtained immediately after the caulking process and contains a certain fraction of volatile matter without being subjected to heat treatment such as calcination or carbonization. ᅳ In the present specification, the term "green coke" or "raw coke" Heat treated products that are calcined or carbonized and volatile components are removed are named as calcined coke.

The D50 particle size of the ground primary particles in step S10 may be 10 or less. If the D50 particle diameter of the primary particles is too large, there may arise a problem that the particle diameter of the secondary particles produced by using the particles is excessively increased or the number of primary particles constituting the unit secondary particles becomes too small. More specifically, the D50 particle size of the primary particles may be 3 to 8 [mu] m.

As described above, since the carbon raw material containing volatile components is pulverized in step S10, primary particles with low roughness can be produced. In addition, since the carbon raw material containing volatile components is pulverized in step S10, primary particles having high sphericity can be produced. At this time, it is a numerical representation that the spherical iris is close to the spherical shape, and the closer it is to 1, the more similar to the spherical shape. Specifically, primary particles having a sphericity of 0.75 to 1 can be prepared. When the sphericity of the primary particles produced by the step S10 is not sufficient, Step < / RTI > When the sphericity of the primary particles satisfies an appropriate range, the tap density becomes large, the rate of electrode expansion becomes small, and the high-speed discharge characteristic becomes excellent. The apparatus for the grinding process is not particularly limited, and a general pulverizer or a modified pulverizer capable of improving the spheroidizing effect and differentiating the pulverizer may be used.

The crusher for crushing the carbon raw material in step S10 is not particularly limited. Specifically, it is possible to use a general type continuous or batch type pulverizer capable of performing jet-mill, roller mill or air classification simultaneously with pulverization.

After step S10, the method may further include a step of raising the primary particles at a rate of 1 to 10 ^° C / minute. The primary particles after the step S10 are present at a normal temperature (10 to 30 ^° C). In order to raise the temperature to the heat treatment temperature for removing volatile components in the primary particles, it is necessary to perform a step of increasing the temperature after step S10. In one embodiment of the present invention, the discharge capacity of the negative electrode active material can be further increased by controlling the rate of temperature rise in the step of increasing the temperature. Specifically, the temperature raising rate may be 1 to 10 ^° C / minute. If the temperature raising rate is too high, the degree of laminating the network or the degree of crystallization may decrease and the discharge capacity may drop.

After the step S10, the step of heat treating the primary particles to remove volatile components in the primary particles may be further included.

The heat treatment temperature may be 800 to 1500 ^° C. If the heat treatment temperature is too low, the volatile components may not be properly removed. If the heat treatment temperature is too high, the effect of removing volatile components is the same, but the equipment configuration and operation cost may increase excessively.

Through the heat treatment step, the primary particles may contain less than 0.5% by weight of volatiles.

Next, in step S20, the primary particles are mixed with a binder to prepare secondary particles. Secondary particles are particles formed by collecting primary particles.

Specifically, in step S20, the binder is added to 100 parts by weight of primary particles, To 20 parts by weight. If the amount of the binder is too small, the binding effect is small and smooth secondary granulation may not be achieved. If the amount of the binder is too large, the capacity and life characteristic of the battery may decrease. The binder may be a coal pitch or a petroleum pitch. . Pitch materials generally have an advantage of being wettable with the surface of the raw carbon material as compared with polymeric binders, and have a merit that they can form a dense bonding interface. The yield of carbonization or graphitization after heat treatment is high, There is an advantage that it can be obtained easily and cheaply. The binder may have a softening point of 80 to 300 ^° C. If the softening point is too low, it is difficult to bond smoothly primary particles and form secondary particles because the binding force is low, and it may be difficult to realize an economical manufacturing process due to low carbonization yield. On the contrary, if the softening point is too high, the operation temperature of the equipment for melting the binder material is high, and the manufacturing cost of the equipment is increased, and heat denaturation and carbonization of some samples may occur due to use at high temperatures.

Step S20 may be performed at a temperature of 110 to 50 CTC for 1 to 5 hours. If the temperature is too low or the time is too short, uniform mixing between the primary particles and the binder may become difficult. If the temperature is too high or the time is too long, the problem of decreasing the capacity and efficiency characteristics of the lumps produced after the final heat treatment process is overcome due to excessive denaturation of the pitch (oxidation and thermal denaturation) Lt; / RTI >

The D50 particle size of the secondary particles produced through step S20 may be 14 to 25. When the D50 particle size of the secondary particles is too small, the specific surface area of the negative electrode active material may be excessively increased, thereby reducing the battery efficiency. On the other hand, when the D50 particle diameter of the secondary particles is too large, it may be difficult to form a secondary battery electrode in which adequate cell performance is exhibited, such as a problem that an electrode layer having an appropriate electrode density is difficult to form because the tap density is excessively low. More specifically, the D50 particle size of the secondary particles may be 16 to 2 m.

The D50 particle size can be controlled through the ratio of the primary particles and the binder, the silver of the step S20, the time, and the kind of the binder.

The equipment for carrying out the step S20 is not particularly limited, The paste-like mixture can be put into equipment that can be mixed at high temperatures. More specifically, the present invention can be carried out by equipping primary particle and binder uniformly using a device for generating a shear force, such as a pair of rotating blades, into a device capable of producing a highly viscous paste-like mixture. If the D50 particle size of the secondary particles produced in step S20 is too large, the particle size can be controlled by pulverizing the particles using a pin mill to remove the particles. The rotation speed (rpm) of the crusher can be adjusted for proper particle size control of the fly ash. However, the present invention is not limited thereto, and various grinding machines can be used to achieve the target particle size.

After step S20, carbonization of the secondary particles may be further included. This removes volatiles from the binder and leads to pyrolysis, solidification and conversion to carbon dioxide. The carbonizing step can be carried out at a temperature of 800 to 1500 ^° C. The atmosphere gas may be an inert gas, and may be performed in a nitrogen or argon atmosphere. The carbonization step can be carried out for 30 minutes to 5 hours.

Next, in step S30, the secondary particles are subjected to liquefaction to produce a hammered material. Step S30 may be performed at a haze of 2800 to 3200 ^° C. The equipment for performing the step S30 is not particularly limited and the Acheson furnace can be used. In general, the softening can be performed according to the operation mode of Acheson without using a separate atmospheric gas, but if an atmospheric gas is used, an inert gas can be used and the operation can be performed in a nitrogen or argon atmosphere. Step S30 may be performed for 30 minutes to 20 days.

After completion of the step S30, the graphite may be pulverized or broken into pulverized materials if necessary.

The negative electrode active material for a lithium secondary battery manufactured through one embodiment of the present invention has a small specific surface area and a high tap density, thereby increasing the densification and energy density of the electrode layer. Specifically, the negative electrode active material for a lithium secondary battery manufactured through one embodiment of the present invention may have a specific surface area of 1.7 m ² / g or less and a tap density of 0.7 g / cc or more. More specifically, it has a specific surface area of 0.8 to 1.6 mVg, The tap density may be 0.8 to 1.0 g / cc.

In another embodiment of the present invention, cathode; And an electrolyte, wherein the negative electrode comprises a negative active material prepared by the above-described method.

Specifically, the electrolyte is at least one selected from the group consisting of fluoro ethylene carbonate (FEC), vinylene carbonate (VC), ethylene sulfonate (ES) Or more of the electrolyte additive.

FEC and the like, the cycle characteristics can be further improved, and a stable solid electrolyte interphase (SEI) can be formed by the electrolyte additive. This fact is supported by the following embodiments.

The characteristics of the negative electrode active material and thus the lithium secondary battery are as described above. In addition, the remaining battery configuration except for the negative electrode active material is generally known. Therefore, a detailed description will be omitted.

Hereinafter, preferred embodiments of the present invention, comparative examples thereof, and evaluation examples thereof will be described. . However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Example 1

As the carbon raw material, green coke (VM content: about 5.0 wt%) as a carbon-based premium acicular coke product was used, and primary coke was prepared by primary crushing the green coke to a degree of D50 of 7 liters using an air clotting mill The pulverized particles were further polished using a pulverizer type pulverizer equipped with an air flow classifier, and the D50 of the obtained primary particles was 7. / m. In FIG. 2, SEM photographs of the primary particles are shown.

The primary particles were heated at a rate of 5 ^° C / min per minute and then heated for 1 hour in a nitrogen atmosphere of i2oo ° c to remove volatile matter. Obtained

Secondary particles were prepared by mixing primary particles with a pitch having a softening point of 120 ^° C in a weight ratio of 100: 10 and using a sieving mixer capable of heating after 2 hours. The D50 of the secondary particles was 19.5 zm. 120 CTC for 1 hour in a nitrogen atmosphere Then, the temperature was raised to 3 ^° C and the mixture was softened for 1 hour to prepare an anode active material. Degree

3 shows SEM photographs of the finally prepared negative electrode active material.

Example 2

The negative electrode active material was prepared in the same manner as in Example 1, except that the heat treatment step for removing volatile components was omitted in Example 1.

Example 3

The negative electrode active material was prepared in the same manner as in Example 1 except that the grinding step was omitted in Example 1. FIG. 4 shows SEM photographs of primary particles in the manufacturing process in Example 3. FIG.

Example 4

The negative electrode active material was prepared in the same manner as in Example 1, except that the weight ratio of the primary particles to the pitch in Example 1 was 100: 20.

Example 5

The negative electrode active material was prepared in the same manner as in Example 1, except that D50 was obtained after grinding and grinding of the primary particles in Example 1.

Example 6

The negative electrode active material was prepared in the same manner as in Example 1, except that the D50 was 5.5 plates after the pulverization and grinding of the primary particles in Example 1.

Example 7

An anode active material was prepared in the same manner as in Example 1, except that the rate of temperature increase after crushing and grinding of the primary particles in Example 1 was controlled to 20 ^° C / min.

Comparative Example 1

The raw coke was used in the same manner as in Example 1 except that the step of carbonizing the primary particles was omitted and the calcined coke used was not used as the green coke used in Example 1 (VM content: about 0.25% by weight) To prepare an anode active material. FIG. 5 shows a scanning electron microscope (SEM) photograph of the ground and pulverized primary particles. As shown in Figs. 2, 4 and 5, when the primary particles in Examples 1 and 3 were compared with the primary particles of Comparative Example 1, the particle surfaces of the primary particles were not sharper and comparatively gentle With the shape of . It can be confirmed that the roughness of the primary particles of Example 1 after crushing and grinding was further reduced as compared with that of the primary particles just pulverized as in Example 3. [

Comparative Example 2

The negative electrode active material was prepared in the same manner as in Comparative Example 1, except that the weight ratio of the calcined coke to the pitch in Comparative Example 1 was 100: 20.

Comparative Example 3

The negative electrode active material was prepared in the same manner as in Comparative Example 1 except that the D50 was 10 after the pulverization and the grinding of the primary particles in Comparative Example 1. [

Experimental Example 1: Measurement of specific surface area and D50 particle size

The specific surface area (BET) and D50 particle diameters of the negative electrode active materials prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were measured and summarized in Table 1 below. The specific surface area was measured by a nitrogen adsorption method.

[Table 1]

As in Example 1 and Example 2, when the primary particles were obtained, the tap density of the negative electrode active material produced through both of the pulverization and the finishing step was generally high and the specific surface area was low. Also, since the particle size of the primary particles increases, the specific surface area of the negative electrode active material produced is generally decreased, It can be confirmed that the particle size of the active material increases proportionally. As the tap density of the negative electrode active material increases, it is expected that the density of the electrode layer is increased and the energy density is increased. Therefore, it can be confirmed that this result can be usefully used for manufacturing a high capacity negative electrode active material.

Experimental Example 2 Preparation of Lithium Secondary Cell (Half-cell) and Measurement of Initial Discharge Capacity and Efficiency

The weight ratio of the negative electrode active material, the binder (Carboxy Methyl Cellulose and styrene Butadiene Rubber) and the conductive material (Super P) prepared in Examples 1 to 7 and Comparative Examples 1 to 3 was 97: 2: 1 Were uniformly mixed using a middle-stream water as a solvent so as to be a negative electrode active material: binder: conductive material.

The resultant mixture was uniformly applied to a copper (Cu) current collector, compressed by a roll press, and vacuum-dried in a 100 ^° C vacuum oven for 12 hours to prepare a negative electrode. At this time, the electrode density was set to 1.4 to 1.6 g / cc.

Li molybdenum (Li-metal) was used as a counter electrode, and 1 mol of LiPF 6 (1 mol) was added to a solvent having a volume ratio of ethylene carbonate (EC: Ethylene Carbonate): dimethyl carbonate ₆ solution was used.

Using each of the above components, a CR 2032 half-coin cell was fabricated according to a conventional manufacturing method.

The batteries were driven under the conditions of 0.1 C, 5 mV, 0.005 C cut-off charging and 0.1 C 1.5 V cut-off discharge, and initial discharge capacity and efficiency were measured and are summarized in Table 2 below.

[Table 2]

Discharge capacity (mAh / g) Efficiency (%)

Example 1 354 93.1

Example 2 353 92.9

Example 3 352 92.9

Example 4 348 92.5

Example 5 354 93.2

Example 6 354 91.2 Example 7 348 93

Comparative Example 1 353 92 Comparative Example 2 347 92.2

Comparative Example 3 353 92.8 Referring to Table 2, the green coke was used as a raw material as in Example 1, and after the pulverization and the polish-pulverizing step were carried out at the time of obtaining the primary particles, the removal of volatile components The discharge capacity and efficiency of the battery were excellent.

On the contrary, as in Example 7, the negative electrode active material after the removal of volatile components under the carbonization condition having a relatively high temperature-raising rate has a relatively low discharge capacity.

As in Example 4, when the amount of the binder material used in the secondary granulation was increased, the discharge capacity of the prepared negative electrode active material decreased.

As in Example 6, when the size of the primary particles was decreased, the efficiency of the battery was decreased because the specific surface area of the negative electrode active material was relatively high and the formation of the passive film was more active.

Experimental Example 3: Measurement of expansion rate and fast discharge characteristic

A battery was prepared by the method described in Experimental Example 2.

The expansion ratio was calculated by calculating the rate of change in thickness of the electrode measured by driving the battery for 10 cycles under the conditions of 0.1 C, 5 mV, 0.005 C cut-of-f lamination and 0.1 C and 1.5 V cut-of f discharging Respectively.

Discharge rate was measured at 3C and 0.2C.

The expansion rate and fast discharge characteristics are summarized in Table 3 below.

[Table 3]

(%) High-speed discharge characteristics (%) Example 1 45 87 Example 2 39 88 Example 3 48 84 Example 4 51 88

Example 5 43 77

Example 6 56 93

Example 7 46 87

Comparative Example 1 58 80

Comparative Example 2 49 74

Comparative Example 3 50 70

As shown in Table 3, it can be seen that the smaller the primary particle size and the secondary particle size of the pulverized particles are, the faster the discharge characteristics are, and the larger the particle size is, the smaller the electrode expansion rate is.

Experimental Example 4: Measurement of fast stratification characteristics

A battery was prepared by the method described in Experimental Example 2.

The high-speed stratification characteristics were evaluated by measuring the initial discharge capacity under the conditions of 0.1 C, 5 mV, 0.005 C cut-off layering, 0.1 C, and 1,5 V cut-off discharge, C, 1.0C, and 2.0C, and the charging and discharging cycles were repeated three times, respectively. The battery charging capacity was measured at 2C and 0.1C.

The fast stratification characteristics are summarized in Table 4 below.

[Table ⁴ ]

Fast Charging Characteristics (%)

Example 1 39.2

Example 2 41.5

Example 3 37.5

Example 4 41.9

Example 5 31.1

Example 6 45.3

Example 7 40.8

Comparative Example 1 35.2

Comparative Example 2 36.4

Comparative Example 3 30.5 Referring to Table 4, it can be seen that the smaller the size of the primary particles and the size of the secondary particles, the higher the superplasticization property.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims

Claims:

[Claim 1]

Pulverizing a carbon raw material containing 4 to 10% by weight of volatile matter to prepare primary particles;

Mixing the primary particles with a binder to prepare secondary particles; And graphitizing the secondary particles to produce a hammered material

And a negative electrode active material for lithium secondary batteries.

[Claim 2]

The method according to claim 1,

Wherein the carbon raw material comprises green coke or raw coke.

[Claim 3]

The method according to claim 1,

Wherein the D50 particle size of the primary particles is 10 L or less.

Claim 4

In Item 1,

Wherein the sphericity of the primary particles is in a range of 0.75 to 1. < RTI ID = 0.0 > 1. < / RTI >

[Claim 5]

In the above,

The method of manufacturing a negative electrode active material for a lithium secondary battery according to claim 1, further comprising a step of crushing the primary particles.

[Claim 6]

In Item 1,

The method for manufacturing a negative electrode active material for a lithium secondary battery according to claim 1, further comprising a step of raising the primary particles at a rate of 1 to 10 ^° C / minute after the step of preparing the primary particles.

[7]

The method according to claim 1, Further comprising the step of heat treating the primary particles to remove volatile components in the primary particles after the step of preparing the primary particles.

8.

In Item 7,

Wherein the step of removing volatile components in the primary particles has a heat treatment temperature of 800 to 150C.

[Claim 9]

The method according to claim 1,

Wherein, in the step of preparing the secondary particles, 2 to 20 parts by weight of the binder is mixed with 100 parts by weight of the primary particles.

Claim 10

The method according to claim 1,

Wherein the binder includes a coal-based pitch or a petroleum-based pitch.

Claim 11

In the above,

Wherein the binder has a softening point of 80 to 300 ^° C.

Claim 12

The method according to claim 1,

Wherein the step of preparing the secondary particles is performed for 1 to 5 hours by utilizing shear force at a temperature of 110 to 500 ^° C.

Claim 13

In Item 1,

Wherein the D50 particle diameter of the secondary particles is 14 to 2 占 퐉 / m.

【Cheolsu port 14】 In the above,

The method of manufacturing a negative electrode active material for a lithium secondary battery according to claim 1, further comprising the step of carbonizing the secondary particles after the step of preparing the secondary particles.

15.

[5] The method of claim 14,

Wherein the carbonizing is performed at a temperature of 800 to 1500 ^° C.

16. The method of claim 16,

The method according to claim 1,

10 _. Wherein the step of preparing the graphite sheet is performed at a temperature of 2800 to 3200 ^° C.

17.

The method according to claim 1,

Wherein the graphite has a specific surface area of 1.7 m ² / g or less and a tap density of 0.7 g / cc or more.

Claim 18

anode; cathode; And an electrolyte,

The lithium secondary battery according to any one of claims 1 to 17, wherein the negative electrode comprises a negative electrode active material for a lithium secondary battery.

20